I notice my 02 Silhouette suddenly do this today. It shifts gear later than its usual timing. Before, it gears up when I reach about 2k to 2.5k RPM. Today it often shifts gear at a bit over 3k RPM. When it shifts, it comes with a short noise like rubber friction. Is tranny dying?

I am not sure if this is related but my silhouette started to idle at higher RPM about 2 weeks ago. The idle speed is not always high, but usually high from cold start. By high, I mean over 2k RPM. Sometimes after a while, it drops to normal speed but sometimes it doesn't.

Welcome to the forums.
May be worthwhile to remove the IAC (intake air control) and try to clean it and port, use throttle body cleaner, especially around the spring & pintle and see if that stabilizes the idle. If not replace the IAC.
The transmission wont shift right if the idle is too high, so get the idle correct first.
You could then have the transmission scanned for stored codes if problems persist.
Have you serviced the transmission with new Dex6 fluid & filter?
How many miles are on your 02 Silhouette?